I have not found any "real point" of studying Astronomy for future reasons, for instance, a job, except for an obvious one which I will explain later. However i have found some information that somewhat answers your question.
The first point is that it was a core subject taught as Hogwarts. This is found on Harry Potter Wiki,
"Astronomy is a core class and subject taught at Hogwarts School of Witchcraft and Wizardry."
The point is that they had to do it. The quote can be found here, first line.
A core class, in case you didn't know is, quote on quote,
"a set of common courses required of all undergraduates and considered the necessary general education for students, irrespective of their choice in major."
Other points that are similar, are that,
"students must study the night skies through their telescopes every Wednesday at midnight and learn the different names of the stars and the movements of the planets."
They "must study" the subject, probably without a choice. Quote found here, under Curriculum, First Year, first line.
Again, another similar point is,
"During the fifth year of studies at Hogwarts, students must study Jupiter's moons and write an essay containing facts such as Europa being covered by ice and Io having many volcanoes"
Again, they "must study", most likely without of choice. Quote found here, under Curriculum, Fifth Year, first line.
And finally, best for last and the most obvious. You would need to know everything about Astronony, if you wanted to teach it! Other professors would probably need to know a small bit of it, just because it may have been on a test, to qualify to become a professor.
I could not find any other purposes, however it is know that to become an Auror, you are recommended (by Minerva) that Defence Against the Dark Arts, Transfiguration, Charms, and Potions would be useful N.E.W.T. level classes for those wishing to pursue a career as an Auror. Note that other skills are required for jobs, this may be the case that Astronomy might be required for other jobs.